A program of research is proposed to investigate the nature of the linguistic and cognitive mechanisms that are disrupted in the various types of writing impairment (dysgraphia) found in patients with focal brain lesions. The program of research is organized in two phases. In the first phase a large group of patients with focal (cerebro-vascular accidents) lesions will be tested with a writing test battery, specially designed to distinguish among various types of writing deficits. Patients' performance on the test battery will be used a) to evaluate a hypothesized model of the writing system; b) to relate functional deficits to site of lesion; and c) to define subgroups of patients with selective deficits involving various basic components of the writing system (e.g., the phoneme-grapheme conversion system, the lexical-semantic system). In the second phase of the research the subgroups defined on the basis of test battery results will be studied extensively using a group/case study methodology. The patients in each group will be tested with a set of experimental tasks designed to elucidate the structure of the linguistic/cognitive mechanism assumed to be disrupted in each of four major patient types - surface, phonological, spelling, and deep dysgraphia. Information generated from the detailed analysis in this phase of the research will be used a) to revise and refine the battery to better discriminate among different patterns of writing impairments; b) to assess specific hypotheses about the cognitive/linguistic bases for particular forms of dysgraphia; and c) to elaborate further the structure of the linguistic and cognitive mechanisms that subserve writing.